From: David Vrabel <david.vrabel@citrix.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>,
Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>,
Peter Zijlstra <peterz@infradead.org>,
virtualization@lists.linux-foundation.org,
Andi Kleen <andi@firstfloor.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Michel Lespinasse <walken@google.com>,
Thomas Gleixner <tglx@linutronix.de>,
linux-arch@vger.kernel.org,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
x86@kernel.org, Ingo Molnar <mingo@redhat.com>,
Daniel J Blueman <daniel@numascale.com>,
xen-devel@lists.xenproject.org,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Alexander Fyodorov <halcy@yandex.ru>,
Arnd Bergmann <arnd@arndb.de>,
Scott J Norton <scott.norton@hp.com>,
Steven Rostedt <rostedt@goodmis.org>,
Chris Wright <chrisw@sous-sol.org>,
George Spelvin <linux@horizon.com>,
Alok Kataria <akataria@vmware.com>,
Aswin Chandramouleeswaran <aswin@hp.com>,
Chegu Vinod <chegu_vino>
Subject: Re: [Xen-devel] [PATCH RFC v5 7/8] pvqspinlock, x86: Add qspinlock para-virtualization support
Date: Mon, 3 Mar 2014 11:06:52 +0000 [thread overview]
Message-ID: <5314624C.8020003@citrix.com> (raw)
In-Reply-To: <530F5EC7.4060603@redhat.com>
On 27/02/14 15:50, Paolo Bonzini wrote:
> Il 27/02/2014 16:22, Raghavendra K T ha scritto:
>> On 02/27/2014 08:15 PM, Paolo Bonzini wrote:
>> [...]
>>>> But neither of the VCPUs being kicked here are halted -- they're either
>>>> running or runnable (descheduled by the hypervisor).
>>>
>>> /me actually looks at Waiman's code...
>>>
>>> Right, this is really different from pvticketlocks, where the *unlock*
>>> primitive wakes up a sleeping VCPU. It is more similar to PLE
>>> (pause-loop exiting).
>>
>> Adding to the discussion, I see there are two possibilities here,
>> considering that in undercommit cases we should not exceed
>> HEAD_SPIN_THRESHOLD,
>>
>> 1. the looping vcpu in pv_head_spin_check() should do halt()
>> considering that we have done enough spinning (more than typical
>> lock-hold time), and hence we are in potential overcommit.
>>
>> 2. multiplex kick_cpu to do directed yield in qspinlock case.
>> But this may result in some ping ponging?
>
> Actually, I think the qspinlock can work roughly the same as the
> pvticketlock, using the same lock_spinning and unlock_lock hooks.
This is is approach I would like to see. This would also work for Xen
PV guests.
The current implementation depends on hardware PLE which Xen PV guests
do not support and I'm not sure if other architectures have something
similar (e.g., does ARM's virtualization extensions have PLE?).
David
next prev parent reply other threads:[~2014-03-03 11:06 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-26 15:14 [PATCH v5 0/8] qspinlock: a 4-byte queue spinlock with PV support Waiman Long
2014-02-26 15:14 ` [PATCH v5 1/8] qspinlock: Introducing a 4-byte queue spinlock implementation Waiman Long
2014-02-26 16:22 ` Peter Zijlstra
2014-02-27 20:25 ` Waiman Long
2014-02-26 16:24 ` Peter Zijlstra
2014-02-27 20:25 ` Waiman Long
2014-02-26 15:14 ` [PATCH v5 2/8] qspinlock, x86: Enable x86-64 to use queue spinlock Waiman Long
2014-02-26 15:14 ` [PATCH v5 3/8] qspinlock, x86: Add x86 specific optimization for 2 contending tasks Waiman Long
2014-02-26 16:20 ` Peter Zijlstra
2014-02-27 20:42 ` Waiman Long
2014-02-28 9:29 ` Peter Zijlstra
2014-02-28 16:25 ` Linus Torvalds
2014-02-28 17:37 ` Peter Zijlstra
2014-02-28 16:38 ` Waiman Long
2014-02-28 17:56 ` Peter Zijlstra
2014-03-03 17:43 ` Peter Zijlstra
2014-03-04 15:27 ` Waiman Long
2014-03-04 16:58 ` Peter Zijlstra
2014-03-04 18:09 ` Peter Zijlstra
2014-03-04 17:48 ` Waiman Long
2014-03-04 22:40 ` Peter Zijlstra
2014-03-05 20:59 ` Peter Zijlstra
2014-02-26 15:14 ` [PATCH RFC v5 4/8] pvqspinlock, x86: Allow unfair spinlock in a real PV environment Waiman Long
2014-02-26 17:07 ` Konrad Rzeszutek Wilk
2014-02-28 17:06 ` Waiman Long
2014-03-03 10:55 ` Paolo Bonzini
2014-03-04 15:15 ` Waiman Long
2014-03-04 15:23 ` Paolo Bonzini
2014-03-04 15:39 ` David Vrabel
2014-03-04 17:50 ` Raghavendra K T
2014-02-27 12:28 ` David Vrabel
2014-02-27 19:40 ` Waiman Long
2014-02-26 15:14 ` [PATCH RFC v5 5/8] pvqspinlock, x86: Enable unfair queue spinlock in a KVM guest Waiman Long
2014-02-26 17:08 ` Konrad Rzeszutek Wilk
2014-02-28 17:08 ` Waiman Long
2014-02-27 9:41 ` Paolo Bonzini
2014-02-27 19:05 ` Waiman Long
2014-02-27 10:40 ` Raghavendra K T
2014-02-27 19:12 ` Waiman Long
2014-02-26 15:14 ` [PATCH RFC v5 6/8] pvqspinlock, x86: Rename paravirt_ticketlocks_enabled Waiman Long
2014-02-26 15:14 ` [PATCH RFC v5 7/8] pvqspinlock, x86: Add qspinlock para-virtualization support Waiman Long
2014-02-26 17:54 ` Konrad Rzeszutek Wilk
2014-02-27 12:11 ` David Vrabel
2014-02-27 13:11 ` Paolo Bonzini
2014-02-27 14:18 ` David Vrabel
2014-02-27 14:45 ` Paolo Bonzini
2014-02-27 15:22 ` Raghavendra K T
2014-02-27 15:50 ` Paolo Bonzini
2014-03-03 11:06 ` David Vrabel [this message]
2014-02-27 20:50 ` Waiman Long
2014-02-27 19:42 ` Waiman Long
2014-02-26 15:14 ` [PATCH RFC v5 8/8] pvqspinlock, x86: Enable KVM to use qspinlock's PV support Waiman Long
2014-02-27 9:31 ` Paolo Bonzini
2014-02-27 18:36 ` Waiman Long
2014-02-26 17:00 ` [PATCH v5 0/8] qspinlock: a 4-byte queue spinlock with " Konrad Rzeszutek Wilk
2014-02-28 16:56 ` Waiman Long
2014-02-26 22:26 ` Paul E. McKenney
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